Pennsylvania National Heritage Program Site Relocated


Fossil Dig

During the planning phase of a bridge reconstruction project on Interstate 81 in November of 2001, PennDOT learned it would be affecting a geologic feature known as the “Swatara Gap Fossil Site,” listed in the PNHP inventory. They were instructed to contact the Pennsylvania Geological Survey, which had oversight responsibility. Soon after, meetings were held to determine how best to minimize damage to the site. Because the site is located on a slope that supports the overlying highway, it figured critically into any road reconstruction plans. Since the highway’s excavation in the late 1960s, the slope had become almost vertical, and this threatened the stability of the highway. Man and nature both played a part in this. In 1990, the site was removed from public access.

Later, to gauge the impact of the steepening slope, over a 6-month period PennDOT studied the natural erosion rates and the effects of unauthorized collecting by the public. PennDOT, JMT Engineers (highway design specialists), and the Survey concluded that no engineering solution was economically feasible that could both preserve the site and maintain the stability of the slope. To adequately secure the road, large quantities of fill material would have to be brought in to cover and regrade the slope, effectively eliminating the site.

In light of this, PennDOT generously offered to remove fossil-bearing material from portions of the slope that would not affect the stability of the highway, and to transport it to nearby Swatara State Park. This amounted to approximately 200 cubic yards of rock, which has now been relocated to Swatara State Park. While the “Swatara Gap Fossil Site” will still remain as a geologic feature listed in the PNHP inventory, the listed location will change. The public and scientists alike will be welcomed to collect, photograph, and marvel at fossil invertebrates that once lived on the Ordovician sea floor some 450 million years ago. Thanks to cooperation among the above groups, all will be able to enjoy this part of our Commonwealth’s geologic heritage for years to come.